import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int m = in.nextInt();

        double tmp1 = fun1(m, n);
        double tmp2 = fun2(0.8, m);
        double tmp3 = fun2(0.2, n-m);
        System.out.printf("%.4f", tmp1 * tmp2 * tmp3);
    }

    public static double fun1(int m, int n) {
        double tmp1 = fun(n);
        double tmp2 = fun(m);
        double tmp3 = fun(n-m);
        return tmp1 / (tmp2 * tmp3);
    }

    public static double fun(int n) {
        if(n == 0) return 1;
        return n * fun(n - 1);
    }

    public static double fun2(double x, int n) {
        if(n == 0) {
            return 1;
        }
        return x * fun2(x, n-1);
    }
}